The present invention concerns a cannula for an eye-surgery instrument. The cannula is employed to shatter the lens of the eye by high-frequency oscillation and to suction out the fragments. The cannula accommodates a suction channel with a section that is wider toward the tip of the cannula.
Cannulas of this type are known and have been demonstrated practical. A cannula of the genus is known from Ophthalmology Times 17, 14 (7/15/1992). The suction channel has an outward-tapering section that tapers conically in toward the suction channel from the aperture at the tip of the needle. The cannula acts on a lens that is to be removed by suctioning larger fragments into the wider opening at the cannula's point, breaking them up without risk to the rest of the eye by aiming a high-frequency ultrasonic wave at the conical surface, and suctioning the smaller fragments on out.
Cannulas with conically tapering sections require less high-frequency power to shatter a lens than cannulas without such sections do. The conical surfaces, however, can be produced only by complex procedures with special tools.